Regarding ASIC reistance, it's a goal that in its strongest form is impossible. You cannot have an ASIC-reistant proof of work, and if someone is trying to tell you otherwise that's a good indicator you're dealing with a crank (or they're trying to sell you something). Anything you can do with a general application-agnostic circuit you can do more efficiently in a specialized circuit. This follows straight from information theory.
HOWEVER, there is a weak form of ASIC-resistance which is interesting to note. With double-SHA256, GPUs are 100-1,000x more efficient than CPUs, FPGAs are 100-1